WASHINGTON (AP) _ The Bush administration underscored its newly positive stance on Syria Monday with praise for Syria's closing its border with Iraq and stopping Iraqi diplomats from boarding flights to Damascus.

With Secretary of State Colin Powell planning to go to Syria in early May bearing an offer to get involved in Mideast peace talks, the administration's line on a country it recently accused of sponsoring terrorism and aiding Saddam Hussein continued to change.

President Bush on Sunday said there were ``positive signs'' that Syria would expel all Iraqi leaders seeking refuge there.

``I believe it when they say they want to cooperate with us,'' Bush said.

On Monday, State Department spokesman Richard Boucher said there had been ``some progress'' on closing the border to everything but humanitarian shipments and ``getting them to take seriously our concerns about individuals who have ended up in Syria.''

And, Boucher said, Syria had refused to permit Iraqi diplomats to board Syria's airline or other fights bound for Damascus.

However, the spokesman also said all Iraqis given haven in Syria had not been identified and that the United States with the cooperation of other nations was trying to make sure the border is closed.

He also said there had been no agreement yet for Syria to return Iraqis wanted for prosecution. ``This is an issue that we'll continue to take up with the Syrian government. Our embassy has been very active in this regard,'' he said.

And, Boucher said, that, after years of monitoring, the United States was still ``highly concerned about Syria's continued acquisition of missile, chemical, biological weapons-related technology, materials, equipment and expertise.''

In Damascus, Foreign Minister Farouk al-Sharaa welcomed Bush's positive remarks and said Syria wanted dialogue and not heated exchanges with the United States.

Al-Sharaa also said anyone crossing the border into Syria would require a visa.

Powell apparently is waiting for the Palestinian prime minister, Mahmoud Abbas, to reach a compromise with Yasser Arafat on a would-be Palestinian government before setting out for the Middle East.

The overall goal is to set in motion creation of a Palestinian state and Israel's withdrawal from territory it won from Egypt, Jordan and Syria in the 1967 Mideast war.

Bush has sought to keep Arafat from retaining control of the Palestinian statehood movement and accused him of being entwined in terrorism.

Arafat's continuing rejection of Abbas' list of proposed ministers indicates he remains in charge.

Without mentioning Arafat by name, Boucher said ``formation of a strong and empowered Palestinian Cabinet headed by Abbas and committed to serious efforts on reform and security is deeply in the interest of the Palestinian people.''

``It's essential the Palestinians complete this process of establishing a government urgently,'' the U.S. official said. ``The United States is doing all we can to help such a government move toward'' Bush's call for a Palestinian state existing in peace alongside Israel, Boucher said.